The box jellyfish of Australia has the most deadly poison in the world. Stings are agonizingly painful and virtually untreatable. The pain from a minor sting can last for days and commonly sends victims into shock. Sufficient contact with a box jellyfish causes death by heart failure.

A zombie apocalypse might not really be possible, but as Hollywood portrays it, life would be grim and short if it ever did. The slow, lumbering zombies of eras past are especially frightening in this case.

Napalm is a mixture of highly flammable gasoline and chemical thickening agent commonly airdropped in Vietnam. It adheres to the skin, is virtually impossible to remove, and causes death by severe burning.

Astronauts routinely conduct spacewalks to repair malfunctions or install new equipment. If the tether were to brake, they would float off into the bleak vacuum of space until their suit ran out of oxygen.